372 research outputs found
Stabilization of quantum metastable states by dissipation
Normally, quantum fluctuations enhance the escape from metastable states in
the presence of dissipation. Here we show that dissipation can enhance the
stability of a quantum metastable system, consisting of a particle moving in a
strongly asymmetric double well potential, interacting with a thermal bath. We
find that the escape time from the metastable state has a nonmonotonic behavior
versus the system-bath coupling and the temperature, producing a stabilizing
effect.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
Culture shapes how we look at faces
Background: Face processing, amongst many basic visual skills, is thought to be invariant across all humans. From as early as 1965, studies of eye movements have consistently revealed a systematic triangular sequence of fixations over the eyes and the mouth, suggesting that faces elicit a universal, biologically-determined information extraction pattern. Methodology/Principal Findings: Here we monitored the eye movements of Western Caucasian and East Asian observers while they learned, recognized, and categorized by race Western Caucasian and East Asian faces. Western Caucasian observers reproduced a scattered triangular pattern of fixations for faces of both races and across tasks. Contrary to intuition, East Asian observers focused more on the central region of the face. Conclusions/Significance: These results demonstrate that face processing can no longer be considered as arising from a universal series of perceptual events. The strategy employed to extract visual information from faces differs across cultures
Social experience does not abolish cultural diversity in eye movements.
Adults from Eastern (e.g., China) and Western (e.g., USA) cultural groups display pronounced differences in a range of visual processing tasks. For example, the eye movement strategies used for information extraction during a variety of face processing tasks (e.g., identification and facial expressions of emotion categorization) differs across cultural groups. Currently, many of the differences reported in previous studies have asserted that culture itself is responsible for shaping the way we process visual information, yet this has never been directly investigated. In the current study, we assessed the relative contribution of genetic and cultural factors by testing face processing in a population of British Born Chinese adults using face recognition and expression classification tasks. Contrary to predictions made by the cultural differences framework, the majority of British Born Chinese adults deployed "Eastern" eye movement strategies, while approximately 25% of participants displayed "Western" strategies. Furthermore, the cultural eye movement strategies used by individuals were consistent across recognition and expression tasks. These findings suggest that "culture" alone cannot straightforwardly account for diversity in eye movement patterns. Instead a more complex understanding of how the environment and individual experiences can influence the mechanisms that govern visual processing is required
NAFLD and Atherosclerosis Are Prevented by a Natural Dietary Supplement Containing Curcumin, Silymarin, Guggul, Chlorogenic Acid and Inulin in Mice Fed a High-Fat Diet
Non-alcoholic fatty liver disease (NAFLD) confers an increased risk of cardiovascular diseases. NAFDL is associated with atherogenic dyslipidemia, inflammation and renin-angiotensin system (RAS) imbalance, which in turn lead to atherosclerotic lesions. In the present study, the impact of a natural dietary supplement (NDS) containing Curcuma longa, silymarin, guggul, chlorogenic acid and inulin on NAFLD and atherosclerosis was evaluated, and the mechanism of action was examined. C57BL/6 mice were fed an HFD for 16 weeks; half of the mice were simultaneously treated with a daily oral administration (os) of the NDS. NAFLD and atherogenic lesions in aorta and carotid artery (histological analysis), hepatic expression of genes involved in the NAFLD (PCR array), hepatic angiotensinogen (AGT) and AT1R mRNA expression (real-time PCR) and plasma angiotensin (ANG)-II levels (ELISA) were evaluated. In the NDS group, steatosis, aortic lesions or carotid artery thickening was not observed. PCR array showed upregulation of some genes involved in lipid metabolism and anti-inflammatory activity (Cpt2, Ifng) and downregulation of some genes involved in pro-inflammatory response and in free fatty acid up-take (Fabp5, Socs3). Hepatic AGT, AT1R mRNA and ANG II plasma levels were significantly lower with respect to the untreated-group. Furthermore, NDS inhibited the dyslipidemia observed in the untreated animals. Altogether, these results suggest that NDS prevents NAFLD and atherogenesis by modulating the expression of different genes involved in NAFLD and avoiding RAS imbalance
Relaxation phenomena in classical and quantum systems
et al.Relaxation phenomena in three different classical and quantum systems are investigated. First, the role of multiplicative and additive noise in a classical metastable system is analyzed. The mean lifetime of the metastable state shows a nonmonotonic behavior with a maximum as a function of both the additive and multiplicative noise intensities. In the second system, the simultaneous action of thermal and non-Gaussian noise on the dynamics of an overdamped point Josephson junction is studied. The effect of a LĂ©vy noise generated by a Cauchy-Lorentz distribution on the mean lifetime of the superconductive metastable state, in the presence of a periodic driving, is investigated. We find resonant activation and noise enhanced stability in the presence of LĂ©vy noise. Finally, the time evolution of a quantum particle moving in a metastable potential and interacting with a thermal reservoir is analyzed. Within the Caldeira-Legget model and the Feynman-Vernon functional approach, we obtain the time evolution of the population distributions in the position eigenstates of the particle, for different values of the thermal bath coupling strength.This work was partially supported by MIUR (Ministero dellâIstruzione dellâUniversitaâ e della Ricerca), CNISM (Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia) and the Russian Foundation for Basic Research (project 11-02-01418). This work was also partially supported by the EU through Grant No. PITN-GA-2009-234970 and the Joint Italian Japanese Laboratory on âQuantum Technologiesâ of the Italian Ministry of Foreign Affairs.Peer Reviewe
Generation of donor-specific T regulatory type 1 cells from patients on dialysis for cell therapy after kidney transplantation
Background. Tregulatory type 1 (Tr1) cell-mediated induction of tolerance in preclinicalmodels of transplantation is remarkably effective. The clinical application of such a therapy in patients on dialysis undergoing kidney transplantation should take into account the possible alterations of the immune systemobserved in these patients. Herein, we aimed at testing the ability to generate donor-specific Tr1 cell-enriched lymphocytes from patients on dialysis on the waiting list for kidney transplantation. Methods. The Tr1 cell-enriched lymphocytes were generated by coculturing interleukin-10-producing dendritic cells obtained from healthy donors with peripheral bloodmononuclear cells (PBMCs) of patients on dialysis, following the same protocol used in a previous cell therapy clinical trial to prevent graft-versus-host disease. Alternatively, purified CD4+ Tcells were used instead of total PBMCs. The ability to generate clinical-grade Tr1 cell-enriched products was defined by testing the reduced response to restimulation withmature dendritic cells generated fromthe original donor (i.e., anergy assay). Results. The Tr1 cell-enrichedmedicinal products generated from PBMCs of patients on dialysis showed a low anergic phenotype, incompatible with their eventual clinical application. This was irrespective of HLA matching with the donor or the intrinsically reduced ability to proliferate in response to alloantigens. On the contrary, the use of purified CD4+ T cells isolated from patients on dialysis led to the generation of a highly anergic donor-specific medicinal product containing an average of 10% Tr1 cells. Conclusions. The Tr1 cell-enriched medicinal products can be efficiently generated from patients on dialysis by carefully tailoring the protocol on the patients' immunological characteristics
Ground state properties of the 2D disordered Hubbard model
We study the ground state of the two-dimensional (2D) disordered Hubbard
model by means of the projector quantum Monte Carlo (PQMC) method. This
approach allows us to investigate the ground state properties of this model for
lattice sizes up to , at quarter filling, for a broad range of
interaction and disorder strengths. Our results show that the ground state of
this system of spin-1/2 fermions remains localised in the presence of the
short-ranged Hubbard interaction.Comment: 7 pages, 9 figure
Dynamics of a Quantum Particle in Asymmetric Bistable Potential with Environmental Noise
In this work we analyze the dynamics of a quantum particle subject to an asymmetric bistable potential and interacting with a thermal reservoir. We obtain the time evolution of the population distributions in both energy and position eigenstates of the particle, for different values of the coupling strength with the thermal bath. The calculation is carried out using the Feynman-
Vernon functional under the discrete variable representation
Delocalizing effect of the Hubbard repulsion for electrons on a two-dimensional disordered lattice
We study numerically the ground-state properties of the repulsive Hubbard
model for spin-1/2 electrons on two-dimensional lattices with disordered
on-site energies. The projector quantum Monte Carlo method is used to obtain
very accurate values of the ground-state charge density distributions with
and particles. The difference in these charge densities allows us
to study the localization properties of an added particle. The results obtained
at quarter-filling on finite clusters show that the Hubbard repulsion has a
strong delocalizing effect on the electrons in disordered 2D lattices. However,
numerical restrictions do not allow us to reach a definite conclusion about the
existence of a metal-insulator transition in the thermodynamic limit in
two-dimensions.Comment: revtex, 7 pages, 7 figure
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